1. Technical Field
The present invention relates to servo control of a magnetic storage device having a magneto resistive head (hereinafter referred to as an "MR head"), and more particularly to a servo burst recording and servo control method for compensating for track shift resulting from the structural properties of the MR head.
2. Related Art
The hard disk drives widely employed as auxiliary storage devices for computer systems have been rapidly and greatly improved in terms of the I/O data processing speed and the data storage capacity. Above all, the development of the MR head serves as an epoch-making step toward high-capacity and high-speed storage devices. Unlike the conventional magnetic inductance heads, the MR head, one of the highly competitive objects of research and development, is hardly affected by disk rotation speed, i.e., the time rate of the magnetic flux change. Therefore, it is an advantage that the magnetic flux change density, i.e., the FCPI (flux change per inch), can be greatly improved, but, on the contrary, it is a drawback that, due to the structural problem of the magneto resistive head, the track density, i.e., TPI (Tracks per Inch), has to be set lower than in the case of the conventional thin film head.
As explained in more detail below, when a conventional MR head is employed, a track shift phenomenon often occurs. The degree of such track shift is often such as to cause problems in utilization of the conventional MR head. Specifically, data transmitted from a host computer cannot normally be written on a desired track due to the track shift phenomenon.
In the prior art, a technique for compensating for track shift is employed. However, the technique of the prior art is ineffective in that, although the amount of track shift can be reduced by one-half, track shift still exists in the positive and negative directions. Thus, there is a need in the prior art for development of a more effective technique for compensating for track shift.
The following U.S. patents are representative of prior art relative to the invention disclosed herein, but are burdened by the disadvantages discussed herein: U.S. Pat. No. 5,668,686 to Shouji et al., entitled Magneto-Resistive Reading Head With Reduced Side-Lobe, U.S. Pat. No. 5,596,463 to Hashimoto, entitled Recording/Reproduction Apparatus With An Integrated Inductive Write, Magnetoresistive Read Head, U.S. Pat. No. 5,594,602 to Isaka et al., entitled Tracking Error Detecting Circuit, U.S. Pat. No. 5,461,517 to Suda et al., entitled Magneto-Resistance Effect Type Of Recording/Reproducing Head, U.S. Pat. No. 5,457,587 to Suzuki, entitled Method And System For Correcting Offset Of Head Position Signal, U.S. Pat. No. 5,455,724 to Suzuki et al., entitled Method Of Compensating Offtrack In Disk Unit, U.S. Pat. No. 5,453,887 to Negishi et al., entitled Head Tracking Servo Pattern, U.S. Pat. No. 5,343,341 to Jahren, entitled Method For Seeking The Center Of A Recorded Data Track, U.S. Pat. No. 5,335,127 to Nagata et al., entitled Lamination Type Magneto-Resistive Head, U.S. Pat. No. 5,212,603 to Hasegawa, entitled Tracking Control Means For A Multi-Channel Reproducing Apparatus, U.S. Pat. No. 5,079,663 to Ju et al., entitled Magnetoresistive Sensor With Track Following Capability, U.S. Pat. No. 4,974,109 to Hohimi et al., entitled Hard Disk Drive Employing A Reference Track To Compensate For Tracking Error, U.S. Pat. No. 4,965,782 to Mathews, entitled Off-Track Bit Shift Compensation Apparatus, U.S. Pat. No. 4,700,244 to Fasen et al., entitled Process And system For Compensating For Information Shifts On Disc Storage Media, and U.S. Pat. No. 4,402,023 to Hiraguri, entitled Tracking Control System In A Magnetic Recording And/Or Reproducing Apparatus.